Throttling device and refrigeration cycle

ABSTRACT

A throttling device is equipped with a valve seat in which a valve port for connecting a primary chamber and a secondary chamber is formed, a needle valve, a needle section which is inserted into the valve port, a guide section for guiding a slide shaft of the needle valve, and a coil spring for biasing the needle valve in a valve-closing direction. The guide section and the coil spring are positioned on the primary chamber side. The coil spring is covered by a stopper section. A gap between the stopper section and a main body case functions as a main body path for delivering a refrigerant from the primary chamber to the valve port.

TECHNICAL FIELD

The present invention relates to a throttling device provided in betweena condenser and an evaporator in a refrigeration cycle of such as an airconditioner, and the refrigeration cycle.

BACKGROUND ART

Conventionally, such a throttling device is disclosed in, for example,JP 4664095 B (Patent Literature 1).

The above conventional throttling device (expansion valve) is athrottling device in which valve opening degree is varied correspondingto a differential pressure between a refrigerant pressure of a condenser(primary side) and a refrigerant pressure of an evaporator (secondaryside) when applied to a refrigeration cycle. This throttling device hasa coil spring biasing a valve body in a valve close direction againstthe differential pressure. Further, the valve-opening degree property isdetermined corresponding to the differential pressure and a springconstant of the coil spring.

CITATION LIST Patent Literature

Patent Literature 1: JP 4664095 B

SUMMARY OF INVENTION Technical Problem

In the throttling device of Patent Literature 1, there is a fear that aforeign particle adhering to the coil spring may prevent the coil springfrom being compressed, and a valve open degree depending on thedifferential pressure may not be obtained. Further, because the coilspring arranged in the primary side of the throttling section isdisposed in a flow path of the fluid, there is a problem that avibration may be generated by the fluid flow.

An object of the present invention is to provide a throttling deviceable to prevent a foreign particle from adhering to a biasing means suchas a coil spring to attain a stable operability, and to prevent a noisefrom occurring by reducing a vibration of the biasing means due to thefluid flow.

Solution to Problem

According to a first aspect of the present invention, there is provideda throttling device provided in between a condenser and an evaporator ina refrigeration cycle for depressurizing a refrigerant in between aprimary chamber connected to the condenser and a secondary chamberconnected to the evaporator to feed the refrigerant to the evaporator,

the throttling device including:

a valve seat in which a valve port for communicating between the primarychamber and the secondary chamber is formed;

a valve body for varying a valve opening degree of the valve port bymoving along an axial line of the valve port;

a guide section for guiding a sliding shaft of the valve body; and

a biasing means for biasing the valve body in a valve closing direction,

wherein the guide section and the biasing means are arranged in theprimary chamber side, and

wherein a cover means covers the biasing means.

According to a second aspect of the present invention, there is providedthe throttling device as described in the first aspect,

further including a pressure-equalizing path for communicating aninterior of the cover means with the primary chamber.

According to a third aspect of the present invention, there is provideda refrigeration cycle including:

a compressor for compressing a refrigerant as a fluid;

a condenser;

an evaporator; and

the throttling device connected in between the condenser and theevaporator as described in first or second aspect.

Effect of the Invention

According to the first aspect of the present invention, because thecover means covers the biasing means, the biasing means such as a coilspring is prevented from an adhesion of foreign particles, and a stableworkability of the biasing means can be attained. Further, a noise isprevented from generating by decreasing a vibration of the biasing meansowing to a refrigerant flow.

According to the second aspect of the present invention, because thethrottling device further includes a pressure-equalizing path forcommunicating an interior of the cover means with the primary chamber,even if the pressure of the primary chamber is rapidly changed, becausethe interior of the cover means is also changed, regardless of a speedof the pressure change, the valve open degree depending on thedifferential pressure can be attained.

According to the third aspect of the present invention, similar to theeffect of the first or second aspect can be attained.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a vertical sectional view showing a valve close state of athrottling device according to a first embodiment of the presentinvention;

FIG. 2 is a vertical sectional view showing a valve open state of thethrottling device according to the first embodiment;

FIG. 3 is a schematic view of a refrigeration cycle according to anembodiment;

FIG. 4A is a sectional view taken on line A-A of FIG. 6B;

FIG. 4B is a vertical sectional view showing a first variation of thefirst embodiment;

FIG. 5A is a sectional view taken on line B-B of FIG. 7B;

FIG. 5B is a vertical sectional view showing a second variation of thefirst embodiment;

FIG. 6 is a vertical sectional view showing a valve close state of athrottling device according to a second embodiment of the presentinvention;

FIG. 7 is a vertical sectional view showing a valve close state of athrottling device according to a third embodiment of the presentinvention; and

FIG. 8 is a vertical sectional view showing a valve close state of athrottling device according to a fourth embodiment of the presentinvention.

DESCRIPTION OF EMBODIMENT

Next, a throttling device according to an embodiment of the presentinvention will be described with reference to drawings. FIG. 1 is avertical sectional view showing a valve close state of a throttlingdevice according to a first embodiment of the present invention, FIG. 2is a vertical sectional view showing a valve open state of thethrottling device according to the first embodiment, and FIG. 3 is aschematic view of a refrigeration cycle according to an embodiment.

First, the refrigeration cycle of FIG. 3 will be described.Incidentally, in FIG. 3, only main components of a throttling device 10are denoted by reference signs. This refrigeration cycle has acompressor 100, a condenser 110, the throttling device of theembodiment, and an evaporator 120. The refrigerant compressed by thecompressor 100 is supplied to the condenser 110, and the refrigerantcooled down by this condenser 110 is fed to the throttling device 10.The throttling device 10 expands and depresses the refrigerant as laterdescribed, and feeds to the evaporator 120. Then, a room interior iscooled down by this evaporator 120 to attain a cooling function. Therefrigerant evaporated by the evaporator 120 is circulated to thecompressor 100. Incidentally, FIG. 3 shows the throttling device 10 ofthe first embodiment, however, the throttling devices 10 of the laterdescribed embodiments and variations similarly constitute therefrigeration cycle.

As shown in FIGS. 1 and 2, the throttling device 10 includes: a mainbody case 1 made of a metal tube such as a copper tube; a valve seatsection 2; a guide section 3; a needle valve 4 as “valve body”; a springreceiver 5 as “receiving member”; a coil spring as “biasing means”; anda stopper section 14 as “cover means”. Incidentally, the valve seatsection 2 and the guide section 3 are integrally formed by cuttingmetallic material or the like.

The main body case 1 has a cylinder shape centering on an axis line L,and constitute a primary chamber 11 connected to the condenser 110 and asecondary chamber 12 connected to the evaporator 120. The valve seatsection 2 has a substantially columnar shape matching with an inner faceof the main body case 1. A swaging groove 2 a is formed on an outerperiphery of the valve seat section 2. By swaging the main body case 1at a position of the swaging groove 2 a, the valve seat section 2 (andthe guide section 3) is fixed to an interior of the main body case 1.

Further, a circular valve port 21 centering on the axis line L is formedon the valve seat section 2, and an open hole 22 opening from the valveport 21 to the secondary chamber 12 side is formed on the valve seatsection 2. The guide section 3 is extended vertically from the valveseat section 2 to an interior of the primary chamber 11. Acylinder-shaped guide hole 31 centering on the axial line L and a cave32 communicating the valve port 21 with the primary chamber 11 areformed on the guide section 3.

The needle valve 4 includes: a columnar-shaped slide shaft 41 insertedinto an interior of the guide hole 31 of the guide section 3; acolumnar-shaped small diameter section 42 of which diameter is smallerthan the slide shaft 41; a conically-shaped needle section 43 of whichdiameter is gradually increased with its extension from the smalldiameter section 42 toward the secondary chamber 12 side; a boss section44 formed at an end of the needle section 43 at the secondary chamber 12side; a fixation section 45 formed on the slide shaft 41 at the stoppersection 14 side; and a truncated conically-shaped abutment section 46 ofwhich diameter is gradually decreased as its extension from the fixationsection 45 toward the stopper section 14 side. a D-cut face 44 a isformed at one point on an outer periphery of the boss section 44.Further, a male thread section 45 a is formed on an outer periphery ofthe fixation section 45, and a swaging groove 45 a is formed on an endof the fixation section 45 at the slide shaft 41 side.

The spring receiver 5 has a cylinder-shaped tube section 51 for fittingwith the needle valve 4, and a flange section 52 formed on an outerperiphery of the tube section 51. A female thread section 51 a forscrewing with the male thread section 45 a of the fixation section 45 isformed on an inner periphery of the tube section 51 at the stoppersection 14 side. This spring receiver 5 is attached to the needle valve4 by fitting the tube section 51 with the needle valve 4 and by screwingthe female thread section 51 a with the male thread section 45 a of thefixation section 45. The attachment position with respect to the needlevalve 4 is adjusted by a screwing amount of the female thread section 51a with respect to the male thread section 45 a. Then, by swaging thetube section 51 at the position of the swaging groove 45 b, the springreceiver 5 is fixed to the needle valve 4. The coil spring 6 is arrangedin between the guide section 3 and the flange section 52 of the springreceiver 5 in a compressed manner. Thereby, the coil spring 6 biases theneedle valve 4 in a valve close direction.

A stopper section 14 has a bottomed cylinder shape composed of acylinder section 14A and a bottom section 14B to form a columnar stopperchamber 141. The cylinder section 14A is fitted with an outer peripheryof the guide section 3. A swaging groove 3 a is formed on an outerperiphery of the guide section 3. By swaging the cylinder section 14A ata position of the swaging groove 3 a, the stopper section 14 is fixed tothe guide section 3. Thereby, the spring receiver 5, the coil spring 6,a part of the slide shaft 41 of the needle valve 4, the fixation section45, and the abutment section 46 are arranged in an interior of thestopper chamber 141. Further, a gap between the stopper section 14 andthe main body case 1 is a main body path 10A for feeding the refrigerantfrom the primary chamber 11 to the valve port 21. A face of the bottomsection 14B at the stopper chamber 141 side is a stopper face 142 onwhich the abutment section 46 of the needle valve 4 abuts. By theabutment section 46 of the needle valve 4 abutting on the stopper face142, a position of the needle valve 4 in the axial line L direction isregulated. Further, a pressure-equalizing hole 143 as“pressure-equalizing path” communicating the stopper chamber 141 withthe primary chamber 11 is formed on the cylinder section 14A.

According to the above configurations, the high-pressure refrigerantfrom the condenser 110 flows into the primary chamber 11. Thisrefrigerant in the primary chamber 11 flows from the cave 32 of theguide section 3 through a gap between the valve port 21 and the needlesection 43 to the open hole 22, and flows out to the secondary chamber12. In the valve close state in FIG. 1, an end face of the abutmentsection 46 of the needle valve 4 abuts on the stopper face 142 of thestopper section 14, and the needle valve 4 is not seated on the valveseat section 2. This gap between the needle section 43 and the valveport 21 works as “orifice” for throttling the flow of the refrigerantfrom the primary chamber 11 to the secondary chamber 12 and forexpanding and depressing the refrigerant. Then, a force generated by thedifferential pressure between the refrigerant pressure in the primarychamber 11 and the refrigerant pressure in the secondary chamber 12 actson the needle valve 4 in the valve open direction. When the pressure inthe primary chamber 11 is increased, the needle valve 4 is in the valveopen state shown in FIG. 2. The balance between the force generated bythe differential pressure and the biasing force of the coil spring 6defines the position of the needle valve, namely, the valve open degreeof the valve port 21.

Here, the refrigerant expanded in the valve port 21 becomes a gas-liquidmixing state in the secondary chamber 12 side, and in the primarychamber 11 side, the refrigerant is a liquid state of the relativelyslow-moving liquid refrigerant. The needle valve 4 is guided along theaxial line L by inserting the slide shaft 41 into the guide hole 31 ofthe guide section 3, and this guide section 3 is arranged in the primarychamber 11 side.

Further, the coil spring 6 and the spring receiver 5 are also arrangedin the primary chamber 11 side, and the stopper section 14 covers thecoil spring 6 together with a part of the slide shaft 41 and a part ofthe guide hole 31. Therefore, the coil spring 6 is prevented from theadhesion of the foreign particle, and a stable operability is attaineduntil the coil spring 6 is compressed most. Further, the noise generatedby the vibration of the coil spring 6 owing to the refrigerant flow isfurther prevented. Further, the refrigerant's effect on the slidemovement between the guide hole 31 and the slide shaft 41 is reduced,and a stable operation of the needle valve 4 is ensured.

In this embodiment, the position of the needle section 43 in the axialline L direction before the valve open degree is increased is positionedby the stopper section 14. Namely, the minimum gap between the valveport 21 and the needle valve 4 as the initial valve open degree definingthe bleed flow rate is defined by the setting positions of the stoppersection 14, the needle valve 4, and the valve seat 2.

Because the needle valve 4 is prevented from seating on the valve seatsection 2 by the stopper section 14, the needle section 43 does not biteinto the valve port 21 due to the biasing force of the coil spring 6 orthe like. Further, because the minimum gap (orifice) between the needlesection 43 and the valve port 21 is secured by the stopper section 14,if the gap is clogged with the foreign particle, the foreign particlecan be ejected by an open operation of the needle valve 4. Namely, in aconfiguration that a bleed port such as a small hole is provided aroundthe valve port or the needle section 43, there is a possibility that theforeign particle is maintained in the clogging state, however, there isno possibility in this embodiment.

Further, the abutment section 46 of the needle valve 4 has a truncatedconical shape, and a diameter of an abutting face abutting on thestopper face 142 of the stopper section 14 is smaller than an outerdiameter of the slide shaft 41. Thereby, even if there is a slightinclination from the axial line L caused by variations of shapes ofcomponents or the like, namely, even if there is a slight variation inaccuracy of a right angle of the needle valve 4 relative to the stopperface 142, a position change of the needle valve 4 in the axial line Ldirection becomes small. Therefore, in particular, even if the needlevalve 4 is rotated from an initial assembled state, an initial bleedarea defining the initial valve open degree will not be changed, and astable bleed flow rate can be attained. In particular, like thisembodiment, this is effective in a case that a distance from the valveport 21 to the stopper face 142 is long by arranging the guide section3, the coil spring 6, and the coil receiver 5 in the primary chamber 11side.

Incidentally, in this embodiment, the boss section 44 of the needlevalve 4 positioned at the primary chamber 12 side has a non-rotationallysymmetric shape by having the D-cut face 44 a. Thereby, the force of therefrigerant passing through the valve port 21 acts unsymmetrically onthe needle valve 4 at both sides of the axial line L to prevent theneedle valve 4 from vibration.

Further, because the stopper section 14 is fixed to the guide section 3,if the main body case 1 is deformed due to a twist of the pipearrangement or the like, the position relationship between the stopperface 142 of the stopper section 14 and the abutment section 46 of theneedle valve will not be sifted, and the performance can be maintained.

Further, because the pressure-equalizing hole 143 is formed on thestopper section 14, if the pressure in the primary chamber 11 is rapidlychanged, the pressure in an interior of the stopper chamber 141 will bealso changed following this pressure change. Therefore, regardless of aspeed of the pressure change, the valve open degree depending on thedifferential pressure can be attained.

FIGS. 4A and 4B show a first variation of the first embodiment, FIGS. 5Aand 5B show a second variation of the first embodiment, and anillustration of the main body case 1 is omitted. FIG. 4A is a sectionalview taken on line A-A of FIG. 4B, and FIG. 5A is a sectional view takenon line B-B of FIG. 5B.

In the first variation shown in FIGS. 4A and 4B, a gap 144 as“pressure-equalizing path” is provided in between the guide section 3and the cylinder section 14A of the stopper section 14. Incidentally, asindicated by a chain line P in FIG. 4A, swaging portions of the cylindersection 14A for fixing the stopper section 14 to the guide section 3 areonly at both sides partially. Thereby, similar to thepressure-equalizing hole 143 of the second embodiment, the gap 144allows the presser in an interior of the stopper chamber 141 to followthe pressure change in the primary chamber 11. Therefore, regardless ofa speed of the pressure change, the valve open degree depending on thedifferential pressure can be attained.

In the second variation shown in FIGS. 5A and 5B, a gap 145 as“pressure-equalizing path” is provided in between the guide section 3and the cylinder section 14A of the stopper section 14 by forming aD-cut face on a part of a side face of the guide section 3. In this casealso, as indicated by a chain line P in FIG. 5A, swaging portions of thecylinder section 14A for fixing the stopper section 14 to the guidesection 3 are only at both sides partially. Thereby, similar to thepressure-equalizing hole 143 of the second embodiment, the gap 145allows the presser in an interior of the stopper chamber 141 to followthe pressure change in the primary chamber 11. Therefore, regardless ofa speed of the pressure change, the valve open degree depending on thedifferential pressure can be attained.

FIG. 6 is a vertical sectional view showing a valve close state of athrottling device according to a second embodiment of the presentinvention. In this second embodiment, a great difference from the firstembodiment is configurations of the guide section and the stoppersection. Hereinafter, in the embodiments and the variations, thecomponents same as or corresponding to the first embodiment are denotedby the same reference signs. These components denoted by the samereference signs have the similar structures and similar effects, and theoverlapping explanations are properly omitted.

A guide section 3′ of this second embodiment has a cylindrical sleeve 3Aas “cover means” extending to an interior of the primary chamber 11.Further, a stopper section 15 forms a columnar-shaped stopper chamber151 by a cylinder section 15A and a bottom section 15B. Further, a faceof the bottom section 15B at the stopper chamber 151 side is a stopperface 152 on which the abutment section 46 of the needle valve 4 abuts.The cylinder section 15A has a swaging groove 15 a, and by swaging thesleeve 3A at a position of the swaging groove 15 a, the stopper section15 is fixed to the guide section 3′. Similar to the first embodiment,the stopper section 15 has the stopper chamber 151, and the springreceiver 5, the coil spring 6, a part of the slide shaft 41 of theneedle valve 4, the fixation section 45, and the abutment section 46 arearranged in an interior of the stopper chamber 151. A gap between thesleeve 3A and the main body case 1 functions as a main body path 10A fordelivering the refrigerant from the primary chamber 11 to the valve port21. Further, a pressure-equalizing hole 156 as “pressure-equalizingpath” communicating the stopper chamber 151 with the primary chamber 11is formed on the cylinder section 15A.

In this second embodiment, because the sleeve 3A of the guide section 3covers the coil spring 6, similar to the first embodiment, the coilspring 6 is prevented from the adhesion of the foreign particle, and astable operability is attained. Further, the noise generated by thevibration of the coil spring 6 owing to the refrigerant flow is furtherprevented. Further, owing to the pressure-equalizing hole 156, withrespect to the pressure rapid change in the primary chamber 11, thevalve open degree depending on the differential pressure can beattained.

Further, in this second embodiment also, because the needle valve 4 isprevented from seating on the valve seat section 2 by the stoppersection 15, the needle section 43 does not bite into the valve port 21.Further, similar to the first embodiment, if the gap is clogged with theforeign particle, the foreign particle can be ejected by an openoperation of the needle valve 4.

FIG. 7 is a vertical sectional view showing a valve close state of athrottling device according to a third embodiment of the presentinvention. In this third embodiment, a valve seat section 2′ and a guidesection 3′ are made of independent members. Further, the stopper sectionis composed of a needle valve 7 and the guide section 3′.

The valve seat section 2′ has a cylinder-shaped sleeve 2A as “covermember” extending to an interior of the primary chamber 11. The guidesection 3′ is arranged in the sleeve 2A, and by swaging the sleeve 2A ata position of the swaging groove 3 a on an outer periphery of the guidesection 3′, the guide section 3′ is fixed to the valve seat section 2′(sleeve 2A). Further, a gap between the sleeve 2A and the main body case1 is a main body path 10A for feeding the refrigerant from the primarychamber 11 to the valve port 21. A cave 23 communicating the valve port21 with the primary chamber 11 is formed on the sleeve 2A, and acylinder-shaped guide hole 31 centering on the axial line L is formed onthe guide section 3′.

The needle valve 7 includes: a columnar-shaped slide shaft 71 insertedinto an interior of the guide hole 31 of the guide section 3′; acolumnar-shaped large diameter section 72 of which diameter is largerthan the slide shaft 71; a conically-shaped needle section 73 of whichdiameter is gradually increased with its extension from the largediameter section 72 toward the secondary chamber 12 side; and a bosssection 74 formed at an end of the needle section 73 at the secondarychamber 12 side. A D-cut face 74 a is formed at one point on an outerperiphery of the boss section 74.

The boss section 81 of the spring receiver 8 is fitted and fixed to anend of the slide shaft 71 of the needle valve 7. Further, the springreceiver 8 has a flange section 82 formed on an outer periphery of theboss section 81. Then, the coil spring 6 is arranged in between theguide section 3′ and the flange section 82 of the spring receiver 8 in acompressed manner. Thereby, the coil spring 6 biases the needle valve 7in a valve close direction. Thereby, the spring receiver 8, the coilspring 6, and a part of the slide shaft 71 of the needle valve 7 arearranged in the sleeve 2A.

Incidentally, a face of the guide section 3′ at the valve port 21 sideis a stopper face 33, and the large diameter section 72 of the needlevalve 7 abuts on this stopper face 33 to regulate the position of theneedle valve 7 in the axils line L direction.

In this third embodiment, because the sleeve 2A and the spring receiver8 cover the coil spring 6, similar to the first embodiment, the coilspring 6 is prevented from the adhesion of the foreign particle, and astable operability is attained. Further, the noise generated by thevibration of the coil spring 6 owing to the refrigerant flow is furtherprevented.

In this third embodiment also, because the needle valve 4 is preventedfrom seating on the valve seat section 2 by the large diameter section72 of the needle valve 7 and the stopper face 33 of the guide section3′, the needle section 73 does not bite into the valve port 21. Further,similar to the first embodiment, if the gap is clogged with the foreignparticle, the foreign particle can be ejected by an open operation ofthe needle valve 7.

FIG. 8 is a vertical sectional view showing a valve close state of athrottling device according to a fourth embodiment of the presentinvention. In this fourth embodiment, a great difference from the secondembodiment is a configuration of the stopper section. In a stoppersection 17 as “cover means” according to the fourth embodiment, acylinder section 17A and a bottom section 17B form a cylinder-shapedstopper chamber 171. Further, a conduction hole 173 is formed at thecenter of the bottom section 17B. Then, by swaging the cylinder section17A at a position of a swaging groove 3 b of the guide section 3′, thestopper section 17 is fixed to the guide section 3′. Further, a gapbetween the stopper section 17 and the main body case 1 is a main bodypath 10A for feeding the refrigerant from the primary chamber 11 to thevalve port 21. Further, in this fourth embodiment, the conduction hole173 is formed on the bottom section 17B, and the tube section 51 of thespring receiver 5 is inserted into the conduction hole 173. Then, a faceof the bottom section 17B at the stopper chamber 171 side is a stopperface 172 on which the flange section 52 of the spring receiver 5 abuts.Thereby, a position of the needle valve 4 in the axial line L directionis regulated.

In this fourth embodiment also, because the stopper section 17 coversthe coil spring 6, similar to the first embodiment, the coil spring 6 isprevented from the adhesion of the foreign particle, and a stableoperability is attained. Further, the noise generated by the vibrationof the coil spring 6 owing to the refrigerant flow is further prevented.

Further, in this fourth embodiment also, because the needle valve 4 isprevented from seating on the valve seat section 2 by the stoppersection 17, the needle section 43 does not bite into the valve port 21.Further, similar to the first embodiment, if the gap is clogged with theforeign particle, the foreign particle can be ejected by an openoperation of the needle valve 4.

In the above embodiments, an example that the valve body is a needlevalve is described. However, the present invention is not limited tothis. The valve body may be a ball valve, a conically shaped valvehaving a large vertex angle, or the like. In this case also, the covermember may cover the biasing means biasing the valve body.

The embodiments of the present invention have been described above indetail with reference to the drawings. However, specific configurationsare not limited to these embodiments, and those with designmodifications or the like within a scope not departing from theprincipal of the present invention are also included in the presentinvention.

REFERENCE SIGNS LIST

1 main body case

11 primary chamber

12 secondary chamber

14 stopper section (cover means)

17 stopper section (cover means)

2 valve seat section

2A sleeve (cover member)

21 valve port

3 guide section

3A sleeve (cover member)

31 guide hole

4 needle valve (valve body)

41 slide shaft

43 needle section

46 abutment section

5 spring receiver (receiving member)

6 coil spring (biasing means)

L axial line

The invention claimed is:
 1. A throttling device provided in between acondenser and an evaporator in a refrigeration cycle for depressurizinga refrigerant in between a primary chamber connected to the condenserand a secondary chamber connected to the evaporator to feed therefrigerant to the evaporator, said throttling device comprising: avalve seat in which a valve port for communicating between the primarychamber and the secondary chamber is formed; a valve body for varying avalve opening degree of the valve port by moving along an axial line ofthe valve port; a guide section having a tubular cover for guiding asliding shaft of the valve body; and a spring biasing the valve body ina valve closing direction, wherein the guide section and the spring arearranged in the primary chamber side, wherein a tubular cover covers thespring, and wherein a force applied to the valve body is generated by adifferential pressure between the primary chamber and the secondarychamber, and wherein the valve open degree is defined by a balancebetween the force generated by the differential pressure in a valve opendirection and a biasing force of the spring in a valve close directionwithout a motor or controller acting on the valve and wherein this valveopen degree determines the flow rate of the refrigerant from the primarychamber to the secondary chamber.
 2. The throttling device as claimed inclaim 1, further comprising a pressure-equalizing path for communicatingan interior of the tubular cover with the primary chamber.
 3. Arefrigeration cycle comprising: a compressor for compressing arefrigerant as a fluid; a condenser; an evaporator; and the throttlingdevice connected in between the condenser and the evaporator as claimedin claim
 1. 4. A refrigeration cycle comprising: a compressor forcompressing a refrigerant as a fluid; a condenser; an evaporator; andthe throttling device connected in between the condenser and theevaporator as claimed in claim 2.